This invention relates to a scroll compressor wherein the oil flow is improved to maximize the amount of oil retained within the compressor.
Scroll compressors are becoming widely utilized in refrigerant compression applications. In a scroll compressor, a first scroll has a base with a generally spiral wrap extending from the base. The first scroll member interfits with a second scroll also having a base with a generally spiral wrap extending from its base. The wraps of the two scrolls interfit to define compression chambers. The second scroll is caused to orbit relative to the first scroll, and as the two move relative to each other the compression chambers decrease in size. A refrigerant is trapped in the compression chambers and is compressed toward a central location on the first scroll member. As the refrigerant reaches a central location it moves through a discharge port and into a discharge pressure chamber.
Scroll compressors are typically mounted in a sealed compressor housing. The sealed compressor housings typically enclose both scrolls and an electric motor for driving the second scroll. Typically, the motor is maintained in a suction chamber which is exposed to the suction refrigerant passing to the compressor. This refrigerant assists in cooling the motor.
Some separation point is defined within the housing to separate the discharge and suction pressure chambers. Often, a separate separator plate is utilized to define the suction and discharge pressure chambers. More recently, other ways of defining the separation area between the suction and discharge pressure chamber have been developed. As one example, the first scroll base has been proposed to separate the two chambers.
Lubricant is important to the operation of a scroll compressor. Thus, an oil sump is typically provided within the sealed housing. Oil passes through the shaft which drives the second scroll, and is delivered to the interface of the first and second scrolls during compression. Thus, there is lubricant mixed with the refrigerant as it is compressed. As the compressed refrigerant leaves the compression chambers, it moves into the discharge pressure chamber. From the discharge pressure chamber, the refrigerant moves downstream to the next component in the refrigerant cycle, the condenser. However, since oil may be mixed with the refrigerant, when the refrigerant leaves the compressor, the oil may migrate with the refrigerant. This is somewhat undesirable, as it is desirable to maintain a sufficient quantity of lubricant in the compressor.
It has been proposed to place oil return lines at various locations in the scroll compressor to return lubricant to the sump. However, the proposals to date have not sufficiently separated and returned oil to the sump from the refrigerant prior to the refrigerant leaving the compressor.
In a disclosed embodiment of this invention, an oil separator is associated with a discharge port of a scroll compressor. The oil separator is preferably a centrifugal oil separator, and the refrigerant with entrained oil is delivered into the centrifugal separator. The combined refrigerant and oil flows through a torturous path, and oil is separated. Preferably, the centrifugal separator has an oil dam to provide an area for buildup of the separated oil. A bleed hole is placed at a location such that the oil in the dam will bleed outwardly and into the discharge pressure chamber. From the discharge pressure chamber a return hole is provided through a separator portion of the scroll compressor which separates the discharge and suction chambers. In a disclosed embodiment, this separator portion is a separator plate; however, as disclosed above, other portions of the scroll compressor can separate the discharge and suction chambers. The return line could be through these other portions in such compressors.
Preferably, the return line is placed at a location upstream from a check valve. At shutdown of the compressor, oil will quickly return to the sump. Thus, the oil bleed hole through the separator portion will fully communicate the suction and discharge chambers. If this bleed hole were downstream of the check valve, then this same communication of pressure would extend to the next component downstream in the refrigerant cycle, the condenser. This would be undesirable. Thus, a check valve is preferably placed downstream of the bleed hole such that at shutdown, the discharge and suction chambers within the compressor will equalize; however, the downstream component of the refrigerant cycle will not equalize in pressure with these chambers.
In alternative ways of maintaining the downstream pressure, the bleed hole is restricted in some fashion. As one example, the bleed hole may be provided with a valve such that the bleed hole is closed when there is no oil to be returned. In one embodiment, the valve may be a float valve that floats to an open position where there is a sufficient quantity of lubricant, but moves to a closed position when there is insufficient lubricant to float the float valve. In another general type of return restriction system, a labyrinth seal is provided to allow oil to return to the sump. However, the same labyrinth path will provide a high resistance to the flow of refrigerant from the discharge to the suction pressure side.
In other embodiments, the return flow could be through the base of the orbiting scroll. Alternatively, the return flow could be through a path which is closed when a refrigerant check valve is closed. In one embodiment, the path extends through the base of the non-orbiting scroll, and has an entry port which is closed by the check valve when in its closed position.
These and other features of this invention can be best understood from the following specification and drawings, the following of which is a brief description.